This thread has at least two new replies, when you load the page it just sits at the top as if you had clicked on the page number only (instead of going to Last Unread like I originally did).
http://www.dakkadakka.com/dakkaforum/posts/list/2340/250857.page#7252895
I think this has happened before, but Lego was tinkering with the code when that happened, though I wouldn't put it past him to be assuaging Dakka's Machine Spirit into working properly, and she's just being a grumpy old birt.